1. Field of the Invention
The present invention relates generally to flat panel display systems. More particularly, the present invention relates to methods and apparatus for backlighting a liquid crystal display (LCD). Even more particularly, the present invention relates to backlighting a LCD on a laptop computer.
2. Description of the Related Art
A conventional laptop computer, such as the laptop computer shown in FIG. 1, utilizes a “fliptop” display to display computer data. The fliptop display is generally perpendicular to the body of the laptop computer when the laptop is in use, allowing the user to view the displayed computer data. When the laptop computer is not in use, the fliptop display is folded down into a closed position so that it is substantially parallel to the body of the computer.
The prior art fliptop display assemblies include a LCD housing. The LCD housing is typically hinged to the body of the laptop computer and generally operates as a protective cover for the LCD module.
Prior art fliptop displays also include a LCD module. The LCD module includes a LCD and a means for “backlighting” the LCD. Backlighting refers to generating light behind the LCD and uniformly projecting it through the LCD. Prior art backlighting techniques generally involve the use of a light source and a light pipe composed of light transmissive material located adjacent to the LCD. U.S. Pat. No. 5,050,946, which is incorporated herein by reference, discusses various light source and light pipe designs.
A cross sectional view of a conventional fliptop display 2 is shown in FIG. 2. As shown in FIG. 2, the conventional fliptop display 2 includes a LCD housing 10 and a LCD module 15. The LCD housing 10 is composed of an opaque material (usually plastic) and protects the LCD module 15. The LCD module 15 is secured within the LCD housing 10 by various common securing means, such as screws, clips, or other frictionally engaging or interlocking means (not shown). Referring again to FIG. 2, the LCD housing 10 has a rear portion 12 and top and bottom portions 11.
Referring again to FIG. 2, the LCD module 15 includes a LCD 20, a light source 25, and a light pipe 30. The aperture 26 of the light source 25 is aligned adjacent to an end of the light pipe 30. As shown in FIG. 2, the light pipe 30 is adjacent to the back surface 21 of the LCD 20. The LCD 20 is backlit when light generated by the light source 25 is conducted through the light source aperture 26 and coupled into an end of the light pipe 30. As shown in U.S. Pat. No. 5,050,946, the coupled light may be uniformly diffused throughout the light pipe 30, and projected toward the back surface 21 of the LCD 20. Some conventional LCD modules utilize a light pipe 30 with a light-reflective coating applied to the back side 31 of the light pipe 30 (not shown). In this manner, light incident upon the back surface 31 of the light pipe 30 will be reflected back into the light pipe 30 for projection toward the LCD 20.
As shown in FIG. 2, the length of the top and bottom portions 11 of the LCD housing 10, and hence the depth D of the fliptop display 2, are roughly defined by the combined thickness of the rear portion 12 of the LCD housing 10 and the LCD module 15.
As shown in FIG. 3, the depth D of the fliptop display 2 is at least the sum of the thickness dl of the rear portion 12 of the LCD housing 10, the diameter d3 of the light source 25, and some fractional portion of the thickness d5 of the LCD 20. In situations where the diameter d3 of the light source 25 is equal to the thickness d4 of the light pipe 30, the depth D may be the sum of the thicknesses dl, d3 (or d4), and d5.
For example, thickness dl of the rear portion 12 of the LCD housing 10 may be 4 mm, the diameter d3 of the light source 25 may be 4 mm and the thicknesses d4 and d5 of the light pipe 30 and the LCD 20 may be 2 mm. As shown in FIG. 3, these dimensions will result in the light source 25 extending 1 mm on either side of the light pipe 30. It can be seen that for this configuration of components, the depth D of the fliptop display 2 will be at least 9 mm and the thickness d2 of the LCD module 15 will be 5 mm. In situations where the diameter d3 of the light source 25 is equal to the thickness d4 of the light pipe 30, the depth D of the fliptop display 2 will be 8 mm and the thickness d2 of the LCD module 15 will be 4 mm.
In the laptop computer industry, it is always desirable to reduce the size and weight of the laptop computer and its component parts. It is also desirable to minimize the number of parts. Thus, there exists a need for a thinner, less complex, and lighter fliptop display.